Add author bio support with AI-generated fallback

[mondominator]

Description

Add author biography information to the author detail page. The layout is already in place (avatar left, text right) - just needs bio data.

Proposed Approach

1. Server-side author entities (primary source)

• Create an authors table with: id, name, bio, photo_url, created_at, updated_at
• Add /api/authors and /api/authors/:name endpoints
• Link audiobooks to author entities

2. External API fallback

• Open Library API (free, has author bios and photos)
• Google Books API
• Cache results server-side to avoid repeated lookups

3. AI-generated fallback (when no data available)

• Use an LLM to generate a brief, factual author bio when:
  • No bio exists in the database
  • External APIs return no results
• Could use OpenAI, Claude, or local models
• Important considerations:
  • Mark AI-generated content clearly ("Bio generated by AI")
  • Keep it factual (birth year, notable works, genre)
  • Allow users to edit/correct
  • Cache generated bios to avoid repeated API calls
  • Consider privacy/accuracy concerns for lesser-known authors

Implementation Notes

• Android app UI is ready - just needs to consume the bio from API
• Bio should support expandable text for long descriptions
• Consider adding author photos (from Open Library or manual upload)

Related

• Closes Author detail page text #61 (Author detail page text) - layout portion complete